Blog post by crypto professor Matthew Green, discussing what Telegram does (I wasn’t familiar with it) and criticizing its cryptography. He says Telegram by default is not end-to-end encrypted. It does have an end-to-end “secret chat” feature, but it’s a nuisance to activate and only works for two-person chats (not groups) where both people are online when the chat starts.
It still isn’t clear to me why Telegram’s founder was arrested. Green expresses some concern over that but doesn’t give any details that weren’t in the headlines.
Not quite
SaaSub is when you have a server do your computing for you. This is just delivering messages. You technically could make a Telegram server if you were motivated enough. The server is just a relay for the most part.
That doesn’t make it good by any stretch.